Define precondition and post-condition to a member function

A precondition is a condition that must be true on entry to a member function. A class is used correctly if preconditions are never false. An operation is not responsible for doing anything sensible if its precondition fails to hold.
For example, the interface invariants of stack class say nothing about pushing yet another element on a stack that is already full. We say that isful()is a precondition of the pushoperation.

Post-condition:

A post-condition is a condition that must be true on exit from a member function if the precondition was valid on entry to that function. A class is implemented correctly if post-conditions are never false.
For example, after pushing an element on the stack, we know that isempty() must necessarily hold. This is a post-condition of the pushoperation.

Ex - 1: What is the output?

int DIM(int array[])
{
return sizeof(array)/sizeof(int );
}
main()
{
int arr[10];
printf(“The dimension of the array is %d”, DIM(arr));
}

Ansr:
1

Explanation:

Arrays cannot be passed to functions as arguments and only the pointers can be passed. So the argument is equivalent to int * array (this is one of the very few places where [] and * usage are equivalent). The return statement becomes, sizeof(int *)/ sizeof(int) that happens to be equal in this case.

Ex - 2: Is there any difference between the two declarations,
1. int foo(int *arr[]) and
2. int foo(int *arr[2])

Ans:
No

Explanation:

Functions can only pass pointers and not arrays. The numbers that are allowed inside the [] is just for more readability. So there is no difference between the two declarations.